The present invention is generally concerned with apparatuses for cleaning thin substrates such as semiconductor wafers, compact discs, flat panel displays and the like. More particularly, the invention is concerned with brush apparatuses for cleaning thin substrates.
For fabrication of semiconductor devices, thin slices or wafers of semiconductor material require polishing by a process that applies an abrasive slurry to the wafer""s surfaces. After polishing, slurry residue is generally cleaned or scrubbed from the wafer surfaces via mechanical scrubbing devices, such as brushes made from porous or sponge like material.
A brush apparatus for cleaning discs is described in co-pending U.S. patent application Ser. No. 09/580,879, filed May 30, 2000 and assigned to the present assignee, entitledxe2x80x9cBrush Core for Disc Scrubbing Apparatus and Method for Use Thereofxe2x80x9d. The entirety of this prior application is incorporated herein by reference.
FIG. 1 is a schematic side perspective view of a scrubbing device 10 for wafer cleaning of the type disclosed in the above-referenced prior patent application. The scrubbing device 10 includes first and second brush rollers, 13a and 13b, which are positioned to contact both sides of a wafer W. A known mechanism 17, such as a motor, is operatively coupled to the first and second brush rollers, 13a and 13b, so as to selectively rotate the first and second brush rollers, 13a and 13b. Also, the wafer W is supported on rotating wheels 19a-19c for both supporting and rotating the wafer W.
In operation the first and second brush rollers 13a and 13b are initially in an open position at a sufficient distance from each other so as to allow a wafer to be inserted therebetween. Thereafter, the wafer W to be cleaned is positioned on the rotating wheels 19a-c between the first and second brush rollers, 13a and 13b, and the brush rollers assume a closed position, sufficiently close to each other so as to both hold the wafer W in place therebetween and to exert a force on the wafer surface adequate to achieve effective cleaning.
Once the brush rollers are in the closed position, the motor 17 is engaged, and the first and second brush rollers, 13a and 13b, begin to spin. Preferably, the brush rollers spin in opposite directions, as indicated by arrows S1 and S2 in FIG. 1, applying forces to the wafer in a downward direction while the wafer rotates, so as to drive the wafer into the rotating wheel 19a-c so that the wafer remains engaged by the rotating wheels.
While the pair of brush rollers spin, the rotating wheels 19a-c which engage the wafer""s edge rotate causing the wafer to rotate. Rotation of the wafer W helps to ensure that the pair of brush rollers thoroughly contact and clean the entire surface of the wafer W. In addition, a cleaning liquid such as de-ionized water is supplied to the wafer surface through perforations in the brush surface to assist in the removal of contaminants.
In FIG. 1, the brushes 13a and 13b have been schematically illustrated as positioned against the wafer W without supporting structure for mounting the brushes. However, as will be recognized by those who are skilled in the art, in a practical embodiment of a wafer scrubber, there must be provided suitable mechanisms for rotatably mounting the brushes in place, transmitting rotary motion to the brushes from a motor, and supplying cleaning liquid to the brushes. According to known techniques, each brush is mounted on a rigid core and a respective mounting assembly is provided to rotatably support each end of the rigid core. One of the mounting assemblies may be motor driven to impart motion to the rigid core and the mounted brush via the driven mounting assembly. The portion of the other mounting assembly which is connected to the rigid core has rotary motion transmitted thereto by the rigid core. It is known to supply cleaning liquid to the brush through the mounting assembly that is not motor driven.
FIG. 2 is a side cross-sectional view showing a brush assembly 20 being installed between brush mounting assemblies 22 and 24. Brush assembly 20 includes a brush 13 mounted on a rigid core or mandrel 26. The brush mounting assemblies 22, 24 respectively have brush mounting supports or spindles 28, 30, to which the core 26 is mounted. The spindles 28, 30 each have a cylindrical profile which allows the spindles to be inserted into the interior 32 of the core 26.
Each of the brush mounting assemblies 22, 24 is mounted on a respective wall (not shown) of a chamber (not shown) of the wafer scrubbing device. It is intended that the brush mounting assemblies 22, 24 be positioned relative to each other such that the respective spindles, 28, 30 are coaxially aligned with each other. Bearings (not separately shown) are provided in the brush mounting assemblies to permit the portions of the assemblies touching the brush assembly to rotate with the brush assembly. As noted before, one of the brush mounting assemblies is motor driven to impart rotational motion to the brush assembly.
In practice, it is difficult to precisely align the brush mounting assemblies so that the respective spindles 28, 30 share a common axis. When the brush mounting assemblies are misaligned, mounting of the brush assembly thereon may cause the brush assembly to bend. In such a case, uneven loads may be placed on the bearings of the brush mounting assemblies, leading to excessive wear of the bearings and premature failure of the brush mounting assemblies. Furthermore, misalignment of the brush mounting assemblies and bending of the brush assembly may cause the brush 13 to be mis-positioned relative to the wafer and to contact the wafer""s surface unevenly. That is, the brush 13 may contact the wafer surface with a greater than desired force, which may result in scratching the wafer surface, or the brush may contact the surface with less than desired force, which may result in insufficient cleaning.
It would accordingly be desirable to provide an improved brush mounting system that addresses the problem of mounting assembly misalignment.
In accordance with the invention, a mounting assembly for a wafer-scrubber brush includes a mounting member adapted to be mounted to a wall of the wafer scrubbing device, a bearing secured to the mounting member, and a brush support rotatably mounted on the bearing. The brush support has an outer end that includes a contact surface adapted to contact a brush mandrel. The contact surface has a spherical profile.
The contact surface may have a convex shape adapted to mate with a concave portion of the brush mandrel, or may have a concave shape adapted to mate with a convex portion of the brush mandrel. The mounting assembly may further include a spring enclosed in the brush support and adapted to bias the outer end of the brush support against the brush mandrel.
The outer end of the brush support may include an extension member that extends outwardly beyond the contact surface and is adapted to limit rotational motion of the outer end of the brush support relative to the brush mandrel.
According to another aspect of the invention, a mandrel adapted to mount a wafer scrubber brush includes a generally cylindrical body. The body has an end adapted to abut a mounting support, and the end includes a contact surface adapted to contact the mounting support. The contact surface has a spherical profile.
According to still another aspect of the invention, a wafer scrubbing device includes a mounting assembly and a brush assembly mounted to the mounting assembly. The mounting assembly and the brush assembly have respective joint portions that mate together to form a spherical joint.
Thus, according to the invention, respective contact portions of the brush mandrel and the brush mounting support have spherical profiles so that a spherical joint is formed between the brush mandrel and the brush mounting support. This arrangement may compensate for misalignment between the two mounting assemblies required to mount the brush and may allow the brush assembly to be mounted between misaligned mounting assemblies without bending the brush assembly. Consequently, uneven loading of the bearings of the brush mounting assemblies may be avoided and the useful life of the brush mounting assemblies may be extended. Furthermore, the brush, when mounted, may be reliably positioned for even contact with the wafer surface, thereby providing for thorough cleaning of the wafer without scratching the wafer.
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims, and the accompanying drawings.